Can Pollution Really Cause Childhood Obesity?

There is significant evidence that exposure to poor levels of air quality between the ages of zero and one can increase the likelihood of childhood obesity, according to a new study from the University of Southern California (USC). The paper found a link between increased rates of obesity and heightened exposure to nitrogen dioxide (NO2), building upon previous studies which have found similar correlations with other contaminants.

Although it’s unknown exactly why the phenomenon occurs, the authors of the paper believe it might be associated with an inflammation of the lungs and other internal body organs, which could potentially have a knock-on effect on things like appetite and metabolism.

“Critical window of exposure”

Published the journal Environmental Health, the USC study followed 2,318 schoolchildren from the region between ages 0 and 10. The results showed that in the first 12 months of life - dubbed the “critical window of exposure” - those who lived nearest to thoroughfares where diesel vehicles were likely to pass (and as such, who were susceptible to the highest amount of NO2 pollution) were on average 1kg heavier than the subjects who suffered the least exposure.

The study’s authors were also cognisant of how other factors could have influenced the anomaly, but said that even accounting for things like ethnicity, gender and social status, it was unlikely that the weight gain was down to anything other than pollution.

A growing body of evidence

The USC study adds to previous research which had suggested obesity could be linked to poor air quality. A 2009 study found a link between increased BMI and proximity to dense traffic in children aged between 10 and 18 years old, while a 2012 investigation found that the children of pregnant mothers exposed to high levels of polycyclic aromatic hydrocarbons (PAHs) were more likely to result in obese children.

More recently, a 2017 paper linked elevated levels of particulate matter 2.5 (PM2.5) with a greater incidence of overweight children. Just this year, another study concluded that high levels of air pollution could result in an increased likely of contracting diabetes in adults. Most concerningly of all, the concentrations of pollution responsible for that increased risk were significantly under the thresholds deemed as “safe” by the World Health Organisation (WHO).

Next generation at risk

The authors of the paper have encouraged parents to heed their findings and exercise greater caution when accompanying their children outside, especially at very young ages. “We would urge parents to be mindful where their young children spend their time, especially considering if those areas are near major roads,” explained Jeniffer Kim, lead author on the study. “The first year of life is a period of rapid development of various systems in the body [and] may prime the body’s future development.”

Aside from keeping abreast of pollution hotspots and tailoring personal habits to avoid the worst affected areas, there is also a call for governments to do more to improve air quality and reduce transport-related pollution. This is especially pertinent in the UK, where the government has been successfully sued three times over its inability or unwillingness to act on the issue.